From: Eric W. Biederman <ebied...@xmission.com>

commit d76cac67db40c172791ce07948367b96a758e45b upstream.

I don't think this is userspace visible but SIGKILL does not have
any si_codes that use the fault member of the siginfo union.  Correct
this the simple way and call force_sig instead of force_sig_fault when
the signal is SIGKILL.

The two know places where synchronous SIGKILL are generated are
do_bad_area and fpsimd_save.  The call paths to force_sig_fault are:
do_bad_area
  arm64_force_sig_fault
    force_sig_fault
force_signal_inject
  arm64_notify_die
    arm64_force_sig_fault
       force_sig_fault

Which means correcting this in arm64_force_sig_fault is enough
to ensure the arm64 code is not misusing the generic code, which
could lead to maintenance problems later.

Cc: sta...@vger.kernel.org
Cc: Dave Martin <dave.mar...@arm.com>
Cc: James Morse <james.mo...@arm.com>
Cc: Will Deacon <will.dea...@arm.com>
Fixes: af40ff687bc9 ("arm64: signal: Ensure si_code is valid for all fault 
signals")
Signed-off-by: "Eric W. Biederman" <ebied...@xmission.com>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 arch/arm64/kernel/traps.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -256,7 +256,10 @@ void arm64_force_sig_fault(int signo, in
                           const char *str)
 {
        arm64_show_signal(signo, str);
-       force_sig_fault(signo, code, addr, current);
+       if (signo == SIGKILL)
+               force_sig(SIGKILL, current);
+       else
+               force_sig_fault(signo, code, addr, current);
 }
 
 void arm64_force_sig_mceerr(int code, void __user *addr, short lsb,


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